The corrosion of molybdenum electrodes in an electric-fired glass melting furnace is generally one of the limiting factors in determining the campaign life of such a furnace. Premature failure of the electrodes necessitates their replacement or a furnace rebuild. DC biasing has been proposed as a means for protecting the heating electrodes in a furnace, especially with the more corrosive glasses. Generally, a source of alternating current is connected to the electrodes for heating and a source of direct current is employed for applying a negative potential to the electrodes. One or several additional electrodes, which act as anodes, are inserted into the furnace for applying the negative potential. These anodes are preferably made of materials which are as insensitive to oxidation as possible, such as platinum. U.S. Pat. No. 2,855,450, issued on Oct. 7, 1958 to Carsten Eden, discloses one arrangement for doing this.
These and other attempts have been made to overcome the effects of cations and anions on the heating electrodes of a glass melting furnace. One item left unsolved by these attemps, however, has been both the protection of the molybdenum heating electrodes and the protection of the platinum anodes.